Traveling wave tube



Feb. 16 1954 I DIEMER 2,669,674

TRAVELING WAVE TUBE Filed July 28, 1949 IN VEN TOR.

Gmsmvs DIEMER,

fi m #4 AGENI Patented Feb. 16, 1954 TRAVELING WAVE TUBE Gesinus Diemer,Eindhoven, Netherlands, as-

signor to Hartford National Bank and Trust Company, Hartford, Conn., astrustee Application July 28, 1949, Serial No. 107,287

Claims priority, application Netherlands September 9, 1948 1 Claim.

This invention relates to arrangements for amplifying centimeter anddecimeter waves, comprising a travelling wave tube, that is an electrontube in which an electron beam is adapted to interact with anelectromagnetic wave adapted to travel along one or a plurality ofhelical conductors.

In order to avoid oscillations, it is known to make the helicalconductor from material of poor electrical conductivity. Moreparticularly if the helical electrode is provided inside the tube, it isalmost impossible afterwards to vary the damping of the helix to bematched to the operating conditions of the tube. The present inventionprovides means for varying the damping, if desired, during the operationof the tube.

According to the invention an arrangement for amplifying centimeter anddecimeter waves, comprising an electron tube in which an electron beamis adapted to interact with an electromagnetic wave adapted to travelalong one or more helical conductors is characterized in that a layer ofa material of poor electrical conductivity, i. e. a material having aresistance of about 0.1 to ohms per cubic centimeter, is provided in thevicinity of the helix and outside the tube. The simplest embodiment ofthe invention is that in which the layer of poor conductivity (forexample graphite obtained from a colloidal solution) is provideddirectly on the outer side of the wall of the tube. The damping may bevaried and be provided at any desired area along the helix by enlargingthe said layer, partly wiping it off or a similar operation. Preferably,however, the layer of the material of poor conductivity is provided on acylinder which is slidable about the tube, so that the damping may beprovided at any desired area, whereas the value of the damping may bevaried by screening part or all of the layer of the material of poorconductivity with respect to the tube by means of a cylinder ofconductive material. If the layer of poor conductivity occupies thewhole surface of the cylinder, the screening operation requires to beeffected by a sliding movement of the conductive cylinder. If, however,the layer of poor conductivity occupies only a portion of the cylinder,the screening effects may be obtained by rotational movement of aconductive part of this cylinder, by which the control of the apparatusduring its use is simplified considerably.

The invention will now be explained more fully by reference to theaccompanying drawing showing diagrammatically, by way of example, partof one embodiment of the arrangement for amplifying centimeter ordecimeter waves according thereto.

In the figure, the reference numeral I designates the glass wall of atube. one end of which contains an incandescent cathode 2. a so-calledWehnelt cylinder 3 and a suction anode 4, which anode 4, duringoperation of the tube, has a positive potential relative to the cathode2. An electron beam is produced which moves in the direction of twocylindrical electrodes 5 which are connected to the exterior and betweenwhich a helix 1 is provided. The electron beam is collected by anelectrode 6. Each extremity of the helix is surrounded by a waveguide 8,9 respectively, provided outside the tube. Between the two waveguidesthe tube is surrounded by a conductive cylinder i0. Reference numeral lldesignates a coil which serves to generate a magnetic field in thedirection of the axis of the tube. The tube is surrounded by a glasscylinder l2, which is internally covered with a layer of graphite. Acopper cylinder I3 is adapted to be introduced into the cylinder I2.Damping may be provided at any desired area of the helix over a lengthnot greater than that of the cylinder I2 by sliding the cylinders I2 andI3 by means of operating members (not shown).

What I claim is:

A travelling wave tube for amplifying short waves comprising a tubularenvelope, 9. conductive helix disposed within said envelope, means todirect an electron beam along the axis of said helix disposed within theenvelope, and means for varying the attenuation of said tube, saidlatter means comprising a hollow cylindrical member outside of andsurrounding said envelope and said helix and adapted to slidethereabout, a layer of a material of poor electrical conductivity on theinner surface of said hollow member, and a second cylindrical member ofconductive material surrounding said envelope and adapted to be insertedinto said hollow member whereby the portions of said layer covered bythe conductive member are screened from the helix.

GESINUS DIEME'R,

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,197,123 King Apr. 16, 1940 2,300,052 Lindenblad Oct. 27,1942 8 Di Toro Dec. 31, 1946 2,541,843 Tiley Feb. 13, 1951 2,575,383Field Nov. 20, 1951 2,585,582 Pierce Feb. 12, 1952 FOREIGN PATENTSNumber Country Date 934,220 France Jan. 7, 1948 OTHER REFERENCES Articleby A. V. Hollenberg, pp. 52-58, Bell System Tech. Jour. for January1949.

